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.Dd $Mdocdate: January 23 2014 $
.Dt RANDOM 4
.Os
.Sh NAME
.Nm random ,
.Nm arandom
.Nd random data source devices
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <dev/rndvar.h>
.Sh DESCRIPTION
The various
.Nm
devices produce high quality random output data.
Entropy data is collected from system activity (such as disk, network,
and clock device interrupts), and then used to key the
ChaCha stream cipher to generate the output.
All the random devices are expected to provide high quality
pseudo-random output data.
.Pp
The
.Xr arc4random 3
function in userland libraries should be used instead, as it works
without the need to access these devices every time.
.Sh FILES
.Bl -tag -width /dev/arandom -compact
.It Pa /dev/random
.It Pa /dev/arandom
.El
.Sh SEE ALSO
.Xr arc4random 3 ,
.Xr md5 3 ,
.Xr random 3 ,
.Xr amdpm 4 ,
.Xr glxsb 4 ,
.Xr pchb 4 ,
.Xr arc4random 9 ,
.Xr md5 9
.Sh HISTORY
A
.Nm
device first appeared in the Linux operating system.
This is a cloned interface.
.Pp
ARC4 routines added by David Mazieres.
Changed to use the ChaCha cipher in
.Ox 5.5 .
.Sh BUGS
No randomness testing suite provided.
